I'm back. RMA'd the motherboard, and still no luck, although the problem is different now. The motherboard now loops rebooting. A green LED on the mobo comes on for maybe five seconds, then powers off, same with all fans. Then this loops. I've tried with different configurations and still nothing. This is getting very frustrating... I've been waiting months for this machine to work and I've simply had the worst luck. Not sure where to go from here.